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Laser Ignition and Flame Temperature for Low-Density Mixtures of Lignite Coal and Pentaerythritol Tetranitrate (Petn)
摘要： We have studied laser ignition (1064 nm, 120 μs) of mixtures of lignite coal (brown coal) particles of size ≤0.1 mm and pentaerythritol tetranitrate (PETN) additives. We established that as the amount of PTEN additives increases in the range 0–50 wt.%, the critical ignition energy density of the mixtures decreases monotonically from 2.9 to 2.0 J/cm2. We used spectral pyrometry to determine that the ?ame temperature for the mixture increases from 1800 K to 2100 K.
关键词： laser ignition,pentaerythritol tetranitrate (PETN),spectral pyrometry,lignite (brown coal),spectroscopy
更新于2025-09-23 15:21:01
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A multi-level optical storage scheme via two-step picosecond laser irradiations: time/space modulations of microstructure and its optical property
摘要： China has a considerable lignite deposit in the Xinjiang province, but surface and underground coal seam fires pose a threat to the resources, environment, economy, and health. As the chemical and physical structure impacts coal fire propensity and behavior, two raw Xinjiang lignites were examined from the Shaerhu (SEH) and Piliqing (PLQ) Collieries. The SEH lignite is more prone to spontaneous combustion (from regional observations). These coals were of the same geological age and were both inertinite-rich 69.8 and 95.6% for SEH and PLQ, respectively (by the point counting approach). The more spontaneous combustion prone lignite had a significantly higher micropore contribution and surface area (92.4% and 195.6 m2/g), while both coals had similar micro- and mesopore size distribution ranges. Despite being classified as lignite by the mean vitrinite random reflectance (Rr, 0.30 and 0.26%) the inertinite contribution displaces some of the structural properties to be similar to the vitrinite-rich, high-volatile bituminous rank. The lignite coals had similar carbon content (74.6 and 78.4 wt % for SEH and PLQ) and vitrinite reflectance but differed in ash, volatile matter, total moisture, and fixed carbon yields. The crystallite parameters [from X-ray diffraction (XRD)], the interlayer spacing, crystallite height, crystallite diameter, and the numbers of aromatic layer indicated the more inertinite-rich coal (PLQ) was slightly less ordered. Both coals were highly aromatic for lignites (fa values of 0.72 and 0.71 for SEH and PLQ), as the inertinite-rich components are more aromatic and polycondensed than huminite-rich (a low rank counterpart of vitrinite) coals of similar reflectance values. Image analysis of high-resolution transmission electron microscopy lattice fringes determined the aromatic fringe length distributions, with contributions between 0.25 and 0.50 nm accounting for 37.1% for PLQ, while SEH had a lower contribution of 28.0% but also a greater contribution of longer fringes (larger polycyclic aromatic hydrocarbon cluster sizes). Image analysis of the lattice fringe orientation and XRD analysis also indicated that the SEH lignite was more ordered. These two coals are potential coals for further exploration of spontaneous combustion behavior for inertinite-rich coals.
关键词： inertinite,lignite,spontaneous combustion,LDIMS,HRTEM,solid-state 13C NMR,XRD
更新于2025-09-19 17:13:59
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Lignite-derived carbon quantum dot/TiO <sub/>2</sub> heterostructure nanocomposites: photoinduced charge transfer properties and enhanced visible light photocatalytic activity
摘要： Here, we present a facile and green route to cleanly and efficiently utilize low-rank lignite to produce in high yields and in situ synthesize CQDs/TiO2 heterostructure nanocomposites. Unlike other CQDs, the lignite-derived CQDs exhibit obvious concentration-dependent red-shifted absorption, unusual aggregation-induced different color emissions and strong orange-red solid-state fluorescence. Through the optimization of the CQD loading proportion, the 2 wt% CQDs/TiO2 shows the optimal photocatalytic performance under visible light. We highlight the CQDs/TiO2 heterostructure nanocomposites by focusing on their dynamic photoinduced charge transfer properties triggered by the heterostructure interface and their application as a photocatalyst under visible light. Our detailed work about the transfer behavior of photoinduced charges in coal-derived carbon quantum dot/TiO2 heterostructure nanocomposites may shed light on the intrinsic reasons for CQD/semiconductor enhanced photocatalytic activity.
关键词： photoinduced charge transfer,heterostructure nanocomposites,visible light photocatalytic activity,lignite-derived carbon quantum dots,TiO2
更新于2025-09-16 10:30:52
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Clear-air lidar dark band
摘要： This paper illustrates measurements carried out by the Raman lidar BASIL in the frame of the HD(CP)2) Observational Prototype Experiment (HOPE), revealing the presence of a clear-air dark band phenomenon (i.e. a minimum in lidar backscatter echoes) in the upper portion of the convective boundary layer. The phenomenon is clearly distinguishable in the lidar backscatter echoes at 532 and 1064 nm, as well as in the particle depolarization data. This phenomenon is attributed to the presence of lignite aerosol particles advected from the surrounding open pit mines in the vicinity of the measuring site. The paper provides evidence of the phenomenon and illustrates possible interpretations for its occurrence.
关键词： convective boundary layer,backscatter echoes,Raman lidar,clear-air dark band,lignite aerosol particles
更新于2025-09-09 09:28:46